Liquid crystal display and substrate thereof

ABSTRACT

Disclosed are a liquid crystal display and a substrate for the same. The substrate comprises first wires formed in one direction on the substrate; second wires intersecting and insulated from the first wires; pixel electrodes formed in pixel regions defined by the first wires and the second wires; and switching elements connected to the first wires, the second wires and the pixel electrodes, wherein an interval between two adjacent second wires has a predetermined dimension that repeatedly varies from one set of adjacent second wires to the next, and a side of the pixel electrodes adjacent to the second wires is shaped in a pattern identical to the second wires such that the pixel electrodes have a wide portion and a narrow portion. The liquid crystal display comprises a first substrate; first wires formed in one direction on the first substrate; second wires intersecting and insulated from the first wires; pixel electrodes formed in pixel regions defined by the crossing of the first wires and the second wires, and a side of the pixel electrodes adjacent to the second wires is shaped in a pattern identical to the second wires such that the pixel electrodes have a wide portion and a narrow portion; switching elements connected to the first wires, the second wires and the pixel electrodes; a second substrate provided opposing the first substrate; a black matrix formed on the second substrate; common electrodes formed on the second substrate; and domain controlling means for controlling the formation of domains of the pixel electrodes.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of co-pending U.S. patent applicationSer. No. 11/066,764, filed on Feb. 28, 2005, which is a continuation ofU.S. patent application Ser. No. 09/935,158, filed on Aug. 23, 2001, nowU.S. Pat. No. 6,870,588 which claims priority to and the benefit ofKorean Patent Application No.: 2000-71681, filed on Nov. 29, 2000, whichare all hereby incorporated by reference in their entireties for allpurposes as if fully set forth herein.

BACKGROUND OF THE INVENTION

(a) Field of the Invention

The present invention relates to a liquid crystal display and asubstrate thereof, and more particularly, to a vertically aligned liquidcrystal display and a substrate thereof in which pixel regions aredivided into a plurality of small domains to obtain a wide viewingangle.

(b) Description of the Related Art

In a liquid crystal display (LCD), liquid crystal material is injectedbetween an upper substrate, on which common electrodes and a colorfilter are formed, and a lower substrate, on which thin film transistorsand pixel electrodes are formed. A voltage of a different potential isapplied to the pixel electrodes and common electrodes to form anelectric field, thereby varying the alignment of liquid crystalmolecules of the liquid crystal material. In this way, the transmittanceof incident light is controlled to enable the display of images.

However, a serious drawback of LCDs is their limited viewing angle.Various methods and configurations have been developed in an attempt toovercome this problem. In one method, the liquid crystal molecules arealigned perpendicularly to the upper and lower substrates, and either apredetermined aperture pattern or protrusions are formed on the pixelelectrodes and the opposing common electrodes.

By forming the aperture patterns on the pixel electrodes and commonelectrodes, a fringe field is generated. Using the fringe field, aslanting direction of the liquid crystal molecules is controlled suchthat the viewing angle is increased. When there are formed protrusionson the pixel electrodes and common electrodes, on the other hand, anelectric field distorted by the protrusions is used to control theslanting direction of the liquid crystal molecules. In an alternativemethod, aperture patterns are formed in the pixel electrodes provided onthe lower substrate and protrusions are formed on the common electrodesprovided on the upper substrate. Using a fringe field generated by theaperture pattern and protrusions, the slanting direction of the liquidcrystal molecules is controlled to form domains.

However, in the above methods, dark portions where light is nottransmitted appear in areas where the aperture patterns and protrusionsare formed. As a result, if an area occupied by the aperture patternsand protrusions is excessively large, brightness is reduced. If thenumber of aperture patterns and protrusions is reduced in an attempt toremedy this problem, the ability to control the slanting of the liquidcrystal molecules is reduced such than an uneven alignment results.Hence, texture is generated and extends over relatively large areas sothat brightness is negatively affected, degrading overall picturequality.

SUMMARY OF THE INVENTION

The present invention has been made in an effort to solve the aboveproblems.

It is an object of the present invention to provide a liquid crystaldisplay in which the size of intervals between apertures or protrusionsis optimized to improve the overall picture quality of the liquidcrystal display.

To achieve the above object, the present invention provides a substratefor a liquid crystal display comprising first wires formed in onedirection on the substrate; second wires intersecting and insulated fromthe first wires; pixel electrodes formed in pixel regions defined by thecrossing of the first wires and the second wires; and switching elementsconnected to the first wires, the second wires and the pixel electrodes,wherein an interval between two adjacent second wires has apredetermined dimension that repeatedly varies from one set of adjacentsecond wires to the next, and a side of the pixel electrodes adjacent tothe second wires is shaped in a pattern identical to the second wiressuch that the pixel electrodes have a wide portion and a narrow portion.

According to a feature of the present invention, the pixel electrodesinclude one or more first apertures dividing the narrow portionfollowing a direction of the second wires, and one or more secondapertures dividing the wide portion following a direction of the firstwires.

According to another feature of the present invention, the substratefurther comprises storage capacitance wires intersecting and insulatedfrom the second wires, and including first branch wires and secondbranch wires overlapping the first apertures and the second apertures,respectively.

According to yet another feature of the present invention, the storagecapacitance wires overlap a boundary between the narrow and wideportions of the pixel electrodes.

According to still yet another feature of the present invention, thefirst apertures divide the narrow portions of the pixel electrodes intotwo equal regions, and the second apertures divide the wide portions ofthe pixel electrodes into three regions, a center region of the threeregions having a width twice or more than outer regions surrounding thecenter region.

In another aspect, the present invention provides a substrate for aliquid crystal display comprising an insulating substrate; gate linesformed on the insulating substrate; storage capacitance lines formed onthe insulating substrate; a gate insulating layer formed over the gatelines and the storage capacitance lines; data lines formed on the gateinsulating layer and intersecting the gate lines and the storagecapacitance lines; a passivation layer formed over the data lines; andpixel electrodes formed on the passivation layer, the pixel electrodeshaving curved edges adjacent to the data lines to have a wide portionand a narrow portion.

According to a feature of the present invention, two adjacent pixelelectrodes with data lines provided therebetween are arranged in anopposite manner, that is, alternating wide positions and narrowportions.

According to another feature of the present invention, the pixelelectrodes include one or more first apertures for dividing the narrowportion following a direction of the data lines, and one or more secondapertures for dividing the wide portion following a direction of thegate lines.

According to yet another feature of the present invention, the storagecapacitance lines intersect and are insulated from the data lines, andinclude first branch lines and second branch lines overlapping the firstand second apertures, respectively.

In yet another aspect, the present invention provides a liquid crystaldisplay comprising a first substrate; first wires formed in onedirection on the first substrate; second wires intersecting andinsulated from the first wires; pixel electrodes formed in pixel regionsdefined by the crossing of the first wires and the second wires, and aside of the pixel electrodes adjacent to the second wires is shaped in apattern identical to the second wires such that the pixel electrodeshave a wide portion and a narrow portion; switching elements connectedto the first wires, the second wires and the pixel electrodes; a secondsubstrate provided opposing the first substrate; a black matrix formedon the second substrate; common electrodes formed on the secondsubstrate; and domain controlling means for controlling the formation ofdomains of the pixel electrodes.

According to a feature of the present invention, the domain controllingmeans includes a first aperture pattern and a second aperture patternformed respectively on the pixel electrodes and the common electrodes.

According to another feature of the present invention, the firstaperture pattern includes first apertures that divide the narrowportions of the pixel electrodes into two equal regions and secondapertures that divide the wide portions of the pixel electrodes intothree regions, and the second aperture pattern includes third aperturesoverlapping the sides of the pixel electrodes in the narrow portionsadjacent to the second wires, fourth apertures overlapping borderregions of the wide portions of the pixel electrodes that areperpendicular to the second wires, and fifth apertures positioned incenter portions between two fourth apertures.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate an embodiment of the invention,and, together with the description, serve to explain the principles ofthe invention:

FIG. 1 is a schematic view of a thin film transistor substrate for aliquid crystal display according to a first preferred embodiment of thepresent invention;

FIG. 2 is a schematic view of aperture patterns formed on commonelectrodes of a liquid crystal display according to a first preferredembodiment of the present invention;

FIG. 3 is schematic plan view of pixel electrodes and aperture patternsof a liquid crystal display according to a first preferred embodiment ofthe present invention;

FIG. 4 is a schematic view taken along line IV-IV′ of FIG. 3;

FIGS. 5 and 6 are schematic views showing examples of aperture patternsfor increasing a viewing angle of a liquid crystal display;

FIG. 7 is a schematic plan view of a pixel electrode and an aperturepattern for a liquid crystal display according to a second preferredembodiment of the present invention; and

FIG. 8 is a schematic plan view of a pixel electrode and an aperturepattern for a liquid crystal display according to a third preferredembodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will now be described indetail with reference to the accompanying drawings.

FIG. 1 shows a schematic view of a thin film transistor substrate for aliquid crystal display according to a first preferred embodiment of thepresent invention; FIG. 2 is a schematic view of aperture patternsformed on common electrodes of a liquid crystal display according to afirst preferred embodiment of the present invention; FIG. 3 is schematicplan view of pixel electrodes and aperture patterns of a liquid crystaldisplay according to a first preferred embodiment of the presentinvention; and FIG. 4 is a schematic view taken along line IV-IV′ ofFIG. 3.

With reference to the drawings, gate lines 114 are formed horizontally(in the drawings) on a lower substrate 100. A storage capacitance line110 is formed in the same direction as the gate lines 114. That is, thestorage capacitance line 110 includes thick portions formed above andbelow an imaginary horizontal line and connected by a connecting portionnarrower than the thick portions. Vertically-extended first and secondbranch electrodes 111 and 112 are connected to the storage capacitancelines 110, and a third branch electrode 113 is connected to the secondbranch electrode 112, the third branch electrode 113 extending in ahorizontal direction.

Formed over the gate lines 114 and the storage capacitance wiring 110,111, 112 and 113 is a gate insulating layer 120. Data lines 130 areformed over the gate insulating layer 120 in a vertical direction (inthe drawings). That is, each data line 130 has an upper and lowerportion, and the upper portion is formed vertically on one side of animaginary vertical line, while the lower portion is formed vertically onan opposing side of the same vertical line. The upper and lower portionsof the data lines 130 are connected by connection portions. Preferably,a distance between imaginary lines extending from adjacent verticaledges of the data lines 130 is 3 μm-20 μm. Also, the data lines 130 areformed over the gate insulating layer 120 in an alternating manner, thatis, with the upper and lower portions provided alternatingly to theright and left of the imaginary vertical lines. Accordingly, spacesbetween the data lines 130 vary between narrow positions and wideportions. The data lines 130 are formed crossing the storage capacitancelines 110 and the gate lines 114, with the crossing of the data lines130 and the storage capacitance lines 110 occurring at the connectionportions.

Formed over the data lines 130 is a passivation layer 140. Further,pixel electrodes 150 are formed on the passivation layer 140 and made ofITO (indium tin oxide) or IZO (indium zinc oxide). In more detail, asingle pixel electrode 150 is provided in each pixel region defined bythe crossing of a pair of gate lines 114 and data lines 130. Also, thepixel electrodes 150 are formed corresponding to the shape of the pixelregions, that is, corresponding to the alternating wide areas and narrowareas of the pixel regions. In the narrow areas of the pixel regions,the pixel electrodes 150 have a first aperture 151 extending verticallysubstantially the entire length of the narrow area of the pixel regions.In the wide areas of the pixel regions, the pixel electrodes 150 have apair of second apertures 152, which extend horizontally. The firstapertures 151 divide the pixel electrodes 150 in the narrow areas of thepixel regions roughly in half, and the second apertures 152 divide thepixel electrodes 150 in the wide areas of the pixel regions into threeregions—two outer regions and a center region. The center region has awidth approximately twice that of the outer regions. Further, the firstapertures 151 overlap the first branch electrodes 111 of the storagecapacitance line 110, and the second apertures 152 overlap the thirdbranch electrodes 113 of the storage capacitance line 110.

A thin film transistor (not shown) is provided in each pixel regioncorresponding to the pixel electrodes 150. A gate electrode of the thinfilm transistors (TFTs) is connected to the gate lines 114, a sourceelectrode of the TFTs is connected to the data lines 130, and a drainelectrode of the TFTs is connected to the pixel electrodes 150. Thesource electrodes and drain electrodes are connected by a semiconductorlayer, which forms channels.

A thin film transistor substrate and an opposing upper substrate willnow be described with reference to FIGS. 2 and 4.

Formed on an inner surface of an insulation substrate 200 (or uppersubstrate) is a black matrix 210, and a red, green, blue color filter220 is formed on the black matrix 210. Further, a passivation layer 230is formed over the color filter 220, and a common electrode 240 isformed on the passivation layer 230. The common electrode 240 is made ofa transparent conductive material such as ITO or IZO. An aperturepattern as shown in FIG. 2 is formed on the common electrode 240. Theaperture pattern includes third apertures 241 extending vertically (inthe drawing), and fourth and fifth apertures 242 and 243 extendinghorizontally (in the drawing), each fifth aperture 243 being formedbetween a pair of fourth apertures 242. The fourth and fifth apertures242 and 243 are provided to the left and right of the third apertures241, and outer edges of the third apertures 241 are indentedcorresponding to ends of the fourth and fifth apertures 242 and 243 toprevent contact between these two elements.

A structure of the thin film transistor substrate 100 and the uppersubstrate 200 in a combined state will now be described with referenceto FIGS. 3 and 4.

The third apertures 241 overlap left and right sides of the narrowportions of the pixel electrodes 150, and the fourth apertures 242overlap upper and lower edges of the wide portions of the pixelelectrodes 150. The fifth apertures 243 are positioned substantially ata center area of the wide portions of the pixel electrodes 150.Accordingly, the narrow portions of the pixel electrodes 150 are dividedinto two small domains by the first apertures 151 and the thirdapertures 241, and the wide portions of the pixel electrodes 150 aredivided into four small domains by the second apertures 152 and thefourth and fifth apertures 242 and 243. It is preferable that a width ofthe small domains is 20±5 μm. If the width of the small domains is toosmall, an aperture ratio is reduced, while too large domains weaken afringe field and make it difficult to control the slanting direction ofthe liquid crystal molecules.

By forming the pixel electrodes 150 together with the apertures 151,152, 241, 242 and 243 for the division of the pixel electrodes 150 intodomains as described above, an aperture ratio that is significantlyimproved over the LCD employing aperture patterns as shown in FIGS. 5and 6, for example, is obtained. That is, aperture ratios of 34% and 36%are realized with the aperture patterns of FIGS. 5 and 6, respectively,while an aperture ratio of 48% is realized with the aperture patternaccording to the first preferred embodiment of the present invention.This is a result of the shape change in the pixel electrodes such thatthe width of the vertical and horizontal domains can be adjusted.

Further, with reference to FIGS. 5 and 6, if an H-shaped commonelectrode wire is arranged incorrectly during manufacture, a portion ofthe common electrode wire becomes present in an area of the pixel regionthrough which light is transmitted. This decreases the aperture ratio.In the LCD of the present invention, on the other hand, the H-shapedcommon electrode wire is not used in order to prevent the occurrence ofthis problem. Further, the majority of the apertures 241, 242 and 243formed on the common electrode are arranged at edges of the pixelregions to minimize a reduction in the aperture ratio. That is, thethird apertures 241 are arranged overlapping the left and right sides ofthe narrow portions of the pixel electrodes 150, and the fourthapertures 242 are arranged overlapping the upper and lower parts of thewide portions of the pixel electrodes 150. These areas then become areascovered by the black matrix 210 or areas where the storage capacitancewires 110 are formed in order to prevent the leakage of light at theborders of these areas. Accordingly, the third and fourth apertures 241and 242 do not additionally reduce the aperture ratio. Additionally, inthe LCD of the present invention, the rectangular shapes of all thedomains both increase in response speed and reduce the texture at theedges of the small domains.

FIG. 7 shows a schematic plan view of a pixel electrode and an aperturepattern for a liquid crystal display according to a second preferredembodiment of the present invention. The LCD according to the secondembodiment is identical to that of the first embodiment except for theshape of various elements. Accordingly, the same reference numerals willbe used. Further, although only a single pixel region is shown in thedrawing, it is to be assumed that each pixel region is configured in thesame manner.

In the second embodiment, a pixel electrode 150 is divided into a narrowportion and a wide portion, identical to the first embodiment. Twosecond apertures 152 are formed in the wide portion of the pixelelectrode 150 such that the wide portion is divided into three regions—acenter region and two outer regions. The center region has a width atleast twice that of the outer regions. Apertures formed on a commonelectrode (not shown) opposing the pixel electrode 150 include a thirdaperture 241 extending vertically (in the drawing), and fourth and fifthapertures 242 and 243 extending horizontally (in the drawing). The fifthaperture 243 is provided between the fourth apertures 242, and the thirdaperture 241 is connected to one of the two fourth apertures 242.

In a state where upper substrate and lower substrate of the LCD arepositioned in an opposing manner, the third aperture 241 divides thenarrow portion of the pixel electrode 150 into two equal regions, andthe fourth apertures 242 are positioned at upper and lower boundaries ofthe wide portion of the pixel electrode 150. Further, the fifth aperture243 is positioned dividing the wide portion of the pixel electrode 150into two equal regions. Accordingly, the narrow portion of the pixelelectrode 150 is divided into two small domains by the third aperture241, and the wide portion of the pixel electrode 150 is divided intofour small domains by the second apertures 152, the fourth apertures242, and the fifth aperture 243. It is preferable that a width of thesmall domains is 20±5 μm. If the width of the small domains is toosmall, an aperture ratio is reduced, while too large domains weaken afringe field and make it difficult to control the slanting direction ofthe liquid crystal molecules.

FIG. 8 shows a schematic plan view of a pixel electrode and an aperturepattern for a liquid crystal display according to a third preferredembodiment of the present invention. The LCD according to the thirdembodiment is identical to that of the first embodiment except for theshape of various elements. Accordingly, the same reference numerals willbe used. Further, although only a single pixel region is shown in thedrawing, it is to be assumed that each pixel region is configured in thesame manner.

In the third embodiment, a pixel electrode 150 is divided into a narrowportion and a wide portion, identical to the first embodiment. A secondaperture 152 is formed horizontally (in the drawing) in the wide portionof the pixel electrode 150, and a sixth aperture 153 is formed at theboundary between the narrow portion and the wide portion of the pixelelectrode 150. The second aperture 152 divides the wide portion of thepixel electrode 150 into two regions. Apertures formed on a commonelectrode (not shown) opposing the pixel electrode 150 include a thirdaperture 241 extending vertically (in the drawing), and two fifthapertures 243 extending horizontally (in the drawing). The fifthapertures 243 are evenly spaced in the region corresponding to the wideportion of the pixel electrode 150.

In a state where upper substrate and lower substrate of the LCD arepositioned in an opposing manner, the third aperture 241 divides thenarrow portion of the pixel electrode 150 into two equal regions, andthe fifth apertures 243 divide the wide portion of the pixel electrode150 into three equal regions. Accordingly, the narrow portion of thepixel electrode 150 is divided into two small domains by the thirdaperture 241, and the wide portion of the pixel electrode 150 is dividedinto four small domains by the second apertures 152 and fifth apertures243. It is preferable that a width of the small domains is 20±5 μm. Ifthe width of the small domains is too small, an aperture ratio isreduced, while too large domains weaken a fringe field and make itdifficult to control a slanting direction of the liquid crystalmolecules.

In the LCD of the present invention structured as in the above, anaperture pattern is provided to optimize the intervals between aperturessuch that a wide viewing angle is obtained and the overall picturequality of the LCD is enhanced.

Although preferred embodiments of the present invention have beendescribed in detail hereinabove, it should be clearly understood thatmany variations and/or modifications of the basic inventive conceptsherein taught which may appear to those skilled in the present art willstill fall within the spirit and scope of the present invention, asdefined in the appended claims.

For example, it is possible to form protrusions instead of theapertures. It is also possible to form a protrusion-aperture mixture,for example, apertures on the pixel electrodes and protrusions on thecommon electrodes.

1. A substrate for a liquid crystal display, comprising: first wiresformed in one direction on the substrate; second wires intersecting andinsulated from the first wires; pixel electrodes formed in pixel regionsdefined by the first wires and the second wires; and switching elementsconnected to the first wires, the second wires and the pixel electrodes,wherein an interval between two adjacent second wires has apredetermined dimension that repeatedly varies from one set of adjacentsecond wires to the next, and a side of the pixel electrodes adjacent tothe second wires is shaped in a pattern identical to the second wiressuch that the pixel electrodes have a wide portion and a narrow portion.